FWIW, I recently encountered an issue where Matlab/Simulink crashed on me and when I restarted my session and tried to re-open the model file I had been working on, Matlab gave a Segmentation Violation.
I'm not sure if anyone else has encountered this, but the problem has something to do with blocks that are interdependent on the CASPER DSP (casper_library.mdl) and BEE_XPS System (xps_library.mdl) block sets, the snap block in my case. If I didn't load the BEE_XPS System blockset, then started Matlab, I could open my file with links broken. I was able to file->open xps_library.mdl and have my design get drawn. I needed to delete the offending interdependent blocks and replace them with ones from the library. I could then save my design and close/open it and continue my project. Xilinx support has been helpful, and have been able to reproduce this problem with my corrupted model file, but are not sure why this would happen in the first place. Either way, the above fix seems to work. Mark